a) Field of the Invention
The invention relates to an adjustable steering column for a motor vehicle, which comprises a steering spindle, a jacket unit bearing the steering spindle, a bracket unit, mountable on the chassis of the motor vehicle, with at least one side jaw, which extends laterally of the jacket unit and supports the jacket unit, an openable and closable securement device, in the closed state of the which the jacket unit is nondisplaceably connected with the bracket unit and in the opened state of which the jacket unit is displaceable with respect to the bracket unit into a displacement direction for the length adjustment of the steering column and into a displacement direction for the height or inclination adjustment of the steering column. The steering column also comprises a clamp bolt penetrating elongated holes in the jacket unit and in the at least one side jaw, as well as at least one bracing part penetrated by the clamp bolt, which bracing part, on the one hand, is connected with the jacket unit displaceably into a first of the displacement directions and nondisplaceably into the second displacement direction and, on the other hand, is connected with the or one of the side jaws displaceably into the second displacement direction and nondisplaceably into the first displacement.
b) Description of Related Prior Art
Such an adjustable steering column is disclosed in DE 103 37 585 A1. The bracing part disposed on the outside of one of the side jaws of the bracket unit includes margin bars extending on both sides of the side jaws in the direction toward the jacket unit, which bars are in contact on the curved narrow sides of the side jaws. Thereby between the side jaw and the bracing part a guide is formed curved about the swivel axis serving for the height or inclination adjustment of the steering column. The margin bars of the bracing part include furthermore pin-like extensions, which, for one, are guided displaceably in an elongated hole cutout extending in the longitudinal direction of the steering column, for another, are guided in contact on the underside of the jacket unit displaceably in the longitudinal direction of the jacket unit. Through the form-fit connection acting in each instance in one of the two displacement directions, between the bracing part and the jacket unit a swivelling out of position of the jacket unit about an instantaneous rotational axis in the region of the clamp bolt and extending parallel to such [bolt] is supported in particular in the event of a crash.
Further adjustable steering columns with form-fittingly acting bracing parts, through which a swivelling out of position of the jacket unit with respect to the bracket unit about an axis in the proximity of the clamp bolt is prevented, are disclosed in U.S. Pat. No. 5,927,152 A1 and DE 102 61 538 A1.
One disadvantage in the case of the known designs is that the bracing parts have a relatively complicated three-dimensional form, which leads to an increase of the production costs. If implemented in the form of a sinter part with extensions projecting from a main plane of the bracing part into a third dimension, risks of tearing-off can occur under the action of a high force, as is the case in the event of a crash.